Tracking down the source of leaks is a pain. It might be from directly above where you detect the water or it may be running along an inner panel from a few feet away. It doesn't take much of a crack or void in your dicor sealant to cause a leak. I would recommend inspecting everything in the vicinity very carefully. Remember to check behind clearance lights, etc in the area as well as they could also be the source of the water intrusion.
If you don't mind spending a couple hundred bucks, many RV dealers will pressure test your TT and inspect all seals using soapy water to detect leaks (looking for bubbles). There are a few threads on a DIY set-up using a leaf blower on this forum if you want to search.
Good luck and stay on top of the leak before any significant damage occurs.
